Metals have been identified as human carcinogens through occupational exposure or as carcinogens in animals through laboratory experimentation. This research proposal is designed to investigate the biological mechanisms which underlie metal carcinogenesis. The individual goals of the two parts of this proposal are: 1. To characterize the biochemical aberrations in DNA synthesis which occur when proliferating human lymphocytes are exposed to metal carcinogens. 2. To determine whether metal carcinogens modify DNA in vivo and in vitro.